1. Field of the Invention
The present invention relates to a cooling fan, and more particularly relates to a cooling fan with a balance structure for maintaining stable rotation of a rotor thereof.
2. Description of Related Art
With the continuing development of the electronic technology, electronic packages such as CPUs (central processing units) are generating more and more heat that requires immediate dissipation. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs.
A conventional cooling fan includes a stator and a rotor having a hub with a plurality of fan blades extending therefrom. The stator establishes an alternating magnetic field interacting with the magnetic field of the rotor to drive the rotor to rotate. Thus rotation of the fan blades generates a forced airflow for cooling the electronic packages, such as the CPUs. The stator includes a bearing defining a bearing hole therein. The rotor has a shaft extending into the bearing hole and is thus rotatably supported by the bearing. However, during rotation of the rotor, the rotating fan blades generate an external pressure which pulls the rotor to move upwardly along the axial direction away from the stator, whereby the rotor is in a somewhat “floating” condition. The floating rotor is inclined to generate a level of noise, which sometimes is unacceptable.
For the foregoing reasons, therefore, there is a need in the art for a cooling fan which overcomes the above-mentioned problems.